1. Field of the Invention
The present invention relates to a liquid crystal display apparatus having a structure in which driving circuit substrates are electrically connected to each other by using a flexible electrode substrate therebetween and an apparatus for manufacturing such liquid crystal display apparatus.
2. Description of the Related Art
A structure of a conventional liquid crystal display apparatus will be explained hereinbelow referring to using a figure showing the display apparatus as seen from a side opposite to the display surface thereof.
FIG. 9 is a plane view showing a structure of the conventional liquid crystal display apparatus as seen from a side opposite to the display surface thereof. As shown in FIG. 9, the conventional liquid crystal display apparatus comprises a liquid crystal display panel 101 composed of two glass substrates having strip electrodes which are orthogonal to each other, pasted so that the strip electrodes of one of the glass substrates confront the strip electrodes of the other of the glass substrates and a certain gap is provided between the two glass substrates to be charged with a liquid crystal; a TAB film 102 mounting a driving IC for driving the liquid crystal display panel 101; a scanning side driving circuit substrate (hereinafter referred to as a "Com-PWB") 103 and a data side driving circuit substrate (hereinafter referred to as a "Seg-PWB") which are both electrically connected to the liquid crystal display panel 101 via the TAB film 102; an upper bezel 110 and a lower bezel (not shown) for supporting the above constituent parts together with each other; and a plastic chassis (not shown).
The liquid crystal display panel 101 has a rectangular flat plate-like configuration. The Seg-PWB 104 has a strip-like configuration and is arranged along a longitudinal direction which is one of the directions of the liquid crystal display panel 101. The Com-PWB 103 has a strip-like configuration and is arranged in a latitudinal direction which is another direction orthogonal to the one direction of the liquid crystal display panel 101. While the Seg-PWB 104 is arranged along the longitudinal direction of the liquid crystal display panel 101 on both sides thereof while the Com-PWB 103 is arranged along the latitudinal direction of the liquid crystal display panel 101 on one side thereof.
In the prior art, for electrical connection between the Com-PWB 103 and the Seg-PWB 104 is used a flexible flat cable (hereinafter referred to as an "FFC") 105, which is cheap in cost, and can be visually aligned with ease.
A structure of connecting the Com-PWB 103 and the Seg-PWB 104 is such that a connection terminal 131 of the Com-PWB 103 and a connection terminal 141 of the Seg-PWB 104 are arranged opposite to each other so that a lead wire of the FFC 105 becomes a straight line, aligning and manually soldering the connection terminals 131 and 141 with the terminal of the FFC 105. The connection terminals 131 and 141 are arranged to have a terminal pitch of 0.8 mm to 1.0 mm so that the connection terminals 131 and 141 can be soldered.
For this purpose, the longitudinal direction of the Seg-PWB 104 has a length equal to the sum total of the addition of the longitudinal direction length of the liquid crystal display panel 101 and the latitudinal direction length of the Com-PWB 103 which stands in parallel to the longitudinal direction of the liquid crystal display panel 101. The Seg-PWB 104 is arranged on both sides of the liquid crystal display panel 101 along the longitudinal direction thereof so as to sandwich the liquid crystal display panel 101 and the Com-PWB 103 therebetween. Then, in the lower bezel, the plastic chassis and the upper bezel 110 supporting the above constituent parts, an attachment holding part 106 for attaching the liquid crystal display apparatus on electronic apparatus such as a personal computer or the like is respectively provided in each corner part thereof. The attachment holding part 106 is provided so as to be located outside of the FFC 105. In FIG. 9, the attachment holding part 106 is provided outside of the Seg-PWB 104 in the longitudinal direction thereof.
Furthermore, Japanese Unexamined Patent Publication JP-A 7-248493 (1995) discloses a structure in which a notch is provided in the corner part of the Seg-PWB 103, and the attachment holding part 106 is positioned in the corner part thereof.
In recent years, there is a stronger demand for reducing the size of the liquid crystal display apparatus. So it is necessary to reduce the size of a part (hereinafter referred to as a window frame) other than the display area of the liquid crystal display apparatus. Thus, circuit components thereof have been gradually reduced in size. However, the conventional liquid crystal display apparatus has a disadvantage in that no attempt can be made to reduce the window frame thereof in size because of the following reasons.
Since the conventional electrical connection of the Com-PWB 103 and Seg-PWB 104 with the FFC 105 by soldering requires a terminal pitch of the FFC 105 of about 0.8 mm to 1.1 mm, a space where the connection terminals 131 and 141 are formed cannot be reduced in size, and the width (the latitudinal direction length) of the Com-PWB 103 and the longitudinal direction length of the Seg-PWB 104 can not be reduced. The prior art liquid crystal display apparatus requires a width of the Com-PWB 103 of about 20 mm to 30 mm in a 10.4 type panel.
Furthermore, in the case where the attachment holding parts 106 are provided on the upper and the lower bezel which support the liquid crystal display panel 101 so as to be located outside of the FFC 105 as shown in FIG. 9, the width of the window frame of the side having the Com-PWB 103 provided thereon, namely a width from the end of the display area on the side of the Com-PWB 103 to the end of the upper or the lower bezel on the side of the Com-PWB 103 will be about 30 mm to 40 mm in the 10.4 type panel.
Even in the structure disclosed in JP-A 7-248493, the width of the Com-PWB 103 cannot be reduced to a sufficiently small level, so that the width of the window frame will be about 25 mm to 35 mm.
Furthermore, in the case where an attempt is made to electrically connect the Com-PWB 103 to the Seg-PWB 104 by using the FFC 105 in the similar manner to that of the prior art, a deviation from the design value which is generated at the time of aligning the Com-PWB 103 and the Seg-PWB 104 cannot be solved.
Furthermore, the soldered connection seen in the prior art has a problem in reliability because of the following reasons; it is difficult to connect narrow pitches by soldering, it is difficult to control the soldering time and the temperature of the tip of the soldering iron which is used for the soldered connection, the completed state of the soldered connection depends on the skill of the worker.
To solve the problem described above, Japanese Unexamined Patent Publication JP-A 5-333358 (1993) discloses a structure in which the Com-PWB 103 and the Seg-PWB 104 are connected to the connection substrate via an anisotropic conductive film and further the connection substrate is connected to a liquid crystal panel via the anisotropic conductive film. JP-A 5-333358 also discloses a technique in which the Com-PWB 103 and Seg-PWB 104 are electrically connected via this connection substrate and the liquid crystal panel.
However, even in the technique disclosed in JP-A 5-333358 described above, there arises a problem in that since each kind of circuit components including large parts such as an aluminum electrolyte capacitors, DC/DC converters or the like are mounted on the Com-PWB 103, these components hinder crimping and connecting the Com-PWB 103 to the connection substrate by the anisotropic conductive film with reliability at the time when the Com-PWB 103 and the connection substrate are connected with an anisotropic conductive film.
On the other hand, it is thought that the Com-PWB 103 and the connection substrate are crimped and connected with the anisotropic conductive film before mounting the circuit components. However, after mounting the circuit components, sit is necessary to perform a reflow process in which the Com-PWB 103 is heated to about 250.degree. C. Thus, there arises a problem in that the reliability in the connection of the anisotropic conductive film is deteriorated.
Furthermore, there is also a problem in that it is very difficult to align the circuit substrate to the liquid crystal panel circuit substrate within the scope of 90 to 100 .mu.m as described in JP-A 5-333358, and the possibility will become high that a pattern deviation is generated.